Paleontologists from Canada have unveiled a newly identified species of a dog-sized pachycephalosaurs. It’s considered the oldest of its kind ever discovered in North America — and quite possibly the world.

Called Acrotholus audeti, the two-legged herbivore roamed the plains of southern Alberta about 85 million years ago. The name is derived from the Greek words for "high dome."

It stood no higher than an adult human’s knee and weighed about 90 lbs (40 kg). Like other pachycephalosaurs, it probably used its dome-shaped skull to head-butt other dinosaurs. Audeti’s skull was composed of solid bone over 4 inches (10 cm) thick.

The discovery was made by David Evans of the Royal Ontario Museum and University of Toronto. He said he was stunned to find a completely intact specimen.

"The species representation of small animals is generally poorer than large animals because the bones of small ones are more susceptible to carnivores and weathering processes," he told CTV News. "The bones of small animals tend to get destroyed before they enter the fossil record."

Evans’s discovery expands our knowledge of pachycephalosaur evolution and their potential diversity. Not much is known about these small dinosaurs, as their fossils are quite rare. But after studying all 600 specimens discovered to date, Evans concluded there were at least 16 varieties of pachycephalosaurs — an indication that these dinosaurs were more diverse and complex than previously thought.

And now, owing to the new discovery, paleontologists are hopeful to find more.